Of course, what originally went to the dogs was … anything decayed and worthless that wasn’t fit for humans, particularly food. This usage was well enough established by the late 18th century for it to have become a metaphorical expression. For example, The London Review of Literature, 1775, included a play called Germanicus, A Tragedy:
“Sirrah, they are prostitutes, and are civil to delude and destroy you; they are painted Jezabels, and they who hearken to ’em, like Jezebel of old will go to the dogs; if you dare to look at ’em, you will be tainted, and if you speak to ’em you are undone.”
Interesting that the phrase has a biblical origin. Jezebel literally went to the dogs for her sins, including an Establishment of Religion in the 400 prophets of Baal she fed at King Ahab’s expense in the days of Elijah the prophet. The question is, are we going to end up on the Elijah side of the Establishment of Religion argument, or on the Ahab/Jezebel side?